Allowance for Loan Losses - Troubled Debt Restructurings (Detail) $ in Thousands	12 Months Ended
Dec. 31, 2016 USD ($) SecurityLoan	Dec. 31, 2015 USD ($) SecurityLoan
Financing Receivable, Modifications [Line Items]
Number \| SecurityLoan	24	23
Pre-mod outstanding principal balance	$ 1,989	$ 3,979
Post-mod outstanding principal balance	2,035	3,973
Financial impact due to TDR taken as additional provision	$ 326	$ 451
Number that defaulted during the period \| SecurityLoan	3	10
Recorded investment of TDRs that defaulted during the period	$ 330	$ 736
Financial impact due to the default of previous TDR taken as charge-offs or additional provisions		$ (9)
Mortgage Loans on Real Estate [Member] \| Residential [Member]
Financing Receivable, Modifications [Line Items]
Number \| SecurityLoan	3	4
Pre-mod outstanding principal balance	$ 650	$ 800
Post-mod outstanding principal balance	656	801
Financial impact due to TDR taken as additional provision	$ 50	$ 8
Number that defaulted during the period \| SecurityLoan	2	4
Recorded investment of TDRs that defaulted during the period	$ 101	$ 221
Mortgage Loans on Real Estate [Member] \| Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number \| SecurityLoan	5	5
Pre-mod outstanding principal balance	$ 423	$ 1,518
Post-mod outstanding principal balance	461	1,517
Financial impact due to TDR taken as additional provision	$ 46	$ (5)
Number that defaulted during the period \| SecurityLoan		2
Recorded investment of TDRs that defaulted during the period		$ 280
Consumer [Member] \| Home Equity Lines of Credit [Member]
Financing Receivable, Modifications [Line Items]
Number \| SecurityLoan	9	2
Pre-mod outstanding principal balance	$ 707	$ 301
Post-mod outstanding principal balance	709	$ 301
Financial impact due to TDR taken as additional provision	$ 205
Number that defaulted during the period \| SecurityLoan	1	3
Recorded investment of TDRs that defaulted during the period	$ 229	$ 182
Consumer [Member] \| Home Equity Loans [Member]
Financing Receivable, Modifications [Line Items]
Number \| SecurityLoan	1	2
Pre-mod outstanding principal balance	$ 105	$ 315
Post-mod outstanding principal balance	$ 105	321
Financial impact due to TDR taken as additional provision		$ 38
Number that defaulted during the period \| SecurityLoan		1
Recorded investment of TDRs that defaulted during the period		$ 53
Financial impact due to the default of previous TDR taken as charge-offs or additional provisions		$ (9)
Consumer [Member] \| Other Consumer [Member]
Financing Receivable, Modifications [Line Items]
Number \| SecurityLoan	2	2
Pre-mod outstanding principal balance	$ 27	$ 89
Post-mod outstanding principal balance	27	89
Financial impact due to TDR taken as additional provision	$ 2	$ 5
Consumer and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Number \| SecurityLoan	4	8
Pre-mod outstanding principal balance	$ 77	$ 956
Post-mod outstanding principal balance	77	944
Financial impact due to TDR taken as additional provision	$ 23	$ 405

Financial Impact due to troubled debt restructure additional provision.

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- Definition

Financial Impact due to troubled debt restructure charge offs or additional provision.

+ References

No definition available.

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+ References

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- Definition

Number of financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953676-111524

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Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

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Pre-modification amount of investment in financing receivables modified by troubled debt restructurings.

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- Definition

Number of financing receivables that have been modified by troubled debt restructurings within the previous 12 months and for which there was a payment default.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953682-111524

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Amount of investment related to financing receivables modified by troubled debt restructurings within the previous 12 months, for which there was a payment default.

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